Lung injury in idiopathic pulmonary fibrosis and measurement of immunoreactive neutrophil elastase and alpha 1-protease inhibitor in blood

Abstract

Idiopathic pulmonary fibrosis (IPF) is thought to develop through slowly progressing lung injury, in which fibrosis occurs as a result of abnormal repair processes. Lung injury in emphysema, in which the normal extracellular matrix is destroyed, is considered to occur mainly because of protease-antiprotease imbalance. In order to examine whether the pathogenesis of IPF involves the proteolytic mechanism of enzymes as in emphysema, concentrations of plasma neutrophil elastase and serum alpha 1-protease inhibitor were measured in patients with IPF, and compared with the levels in patients with emphysema and in normal individuals. In some patients with IPF, the blood concentration of neutrophil elastase was much higher than normal and the degree of imbalance between neutrophil elastase and alpha 1-protease inhibitor was significantly great than in patients with emphysema. In these patients, many years had passed since the onset of the disease, the number of leukocytes and neutrophils and the concentration of LDH in peripheral blood were significantly higher than normal, and the concentration of CEA-II was slightly increased. These data suggest that chronic, massive lung injury had occurred. The blood concentration of neutrophil elastase and alpha 1-protease inhibitor ratio may be useful in assessing the degree of lung injury.